Combined broadcast receiving and telephone system



March 9 1926; 1,576,308

- E. E. CLEMENT COMBINED BROADCAST RECEIVING AND TELEPHONE SYSTEM FiledOct. 27, 1922 2 Sheets-Sheet 1 67 13- w @k Mg 2 i 3 Allll 265 iAmplifier Dingo: AN 0 AMPLIFIER 360 I. mmprmcv 1E.. E. CLEMENT COMBINEDBROADCAST RECEIVING AND TELEFH ONE SYSTEM March 9, 1926.

- Filed Oct 27 1922 2 Sheets-Sheet 2 TELEYIOME 1/:

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gwwnto o Patented Man 9, 1926,,

v srArEs EDWARD E, CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA,ASSIGNOR TO ED- WARD F. COLLADAY, OF WASHINGTON, DISTRICT OF COLUMBIA.

COMBINED BRGADCAST RECEIVING AND TELEPHONE SYSTEM.

Application filed October 27, 1922. Serial No. 597,422..

To all whom it may concern:

Be it known that I, EDWARD E. Cnniunn'i, citizen of the United States,residing at \Vashington, in the District of Columbia, have inventedcertain new and useful Improvements in Combined Broadcast Receiving andTelephone Systems, of which the following is a specification, referencebeing had therein to the accompanying drawing.

My invention relates to radio broadcast distributing systems and moreparticularly to a combined radio broadcast in distributing and telephonesystem. i

The object of the present invention is to provide a simple and effectivesystem for distributing or relaying broadcast waves from a centralotiicc to subscribers, with supervision at the central oilicc of thereception at any subscribers substation. and to accomplish this resultwithout additional line conductors and without change in the telephoneexchange plant proper.

I attain my object by receiving modulated broadcast carrier waves at thecentral station, amplifying and distributing the same at superaudiofrequencies over the subscribers wired lines, demodulating the carriersat the subscribers stations and when desired sending back the resultantaudio frequency waves over any subscribers line to central. where theymay be caused to energize a suitable audio frequency receiver forpurposes of observation, supervision and test. The subscribersinstruments are standordinary telephone desk set; Fig. 5 is adiagrammatic view of the same showing the circuit connections. Figs. 5and 5 are views similar to Fig. 5, showing radio ampl1 fication andaudio amplification respectively on the line side of the coupler,whereby the desk set is reduced to its simplest elements.

Referring to the drawings, in Fig. 1, the

, apparatus to the left of the vertical dotted lines is situated at thecentral oflice, that to the right is at the subscribers station whilethe connection indicated between the dotted lines is the lineconnection.

The telephone exchange system assumed herein to be used in carrying outmy invention is the standard Western Electric No. 1 switchboard circuitwith the usual standard Western Electric substation apparatus.

The part of the usual telephone exchange system here shown comprises thesubscriberfs' substation apparatus A connected by conductors 1 and 2 tothe conductors 3 and 42 of the line B terminating at the central officeC through the wires 5 and 6 on multiple jacks 7. Radio broacast wavesfrom other stations are received at the telephone central station C bythe receiving or antenna circuit 8, from which the broadcast waves areamplified and relayed onto the wires 3-4 of the subscribers line circuitB through known or other suitable amplifying and coupling means such asthe amplifying system indicated at 9 and the switch 10. Other switchessuch as 11 are connected with the amplifier 9 in multiple with theswitch 10 scribers line extension 56.

Either relayed orlocal broadcast is. put on to the subscribers lines atsuper-audio frequency and at sufiicient amplitude to enable demodulationto be accomplished and effective audio frequency currents to be therebyproduced at the subscribers substations with simple detector sets whichmay be of any known or other suitable form such as the crystal detectortype, indicated at 18. The

detector circuit 18 is arranged to be connected with either thetelephone head set 19 or the supervisory coupling means 20, through adouble-pole double-throw switch 21, at the will of the subscriber. Theuse of the dcublethrcw swltch has the advantage of efiecting anautomatic disconnection of thehead telephone 19 upon connectionct thedetector circuit with the test coupling so that all the energ will gointo the latter, although, if desi ed, the head telephone may bepermanently connected and the test coupling simply connected in shuntwhen wanted.

To enable the .reception at the subscribers substation to be supervisedfrom the central oflice, a supervisory circuit 22 is provided at thecentral ofiice arranged to be connected with any su-bscribers linethrough suitable switching means such as t-heplug 23 adapted to engagewith a jack such as 24 connected in multiple'to the subscriberslineextension 5-6. The supervisory C11- cii-it 22 may be of any suitabletype, preferably that used with the Western Electric No. 1 switchboardsystem, the essentials being that it contains means for calling thesubscriber suchas the ringing key 25, and

a listening and talking set 26 and listening 'key 27. The supervisory.coupling 20 at the subscribers substation is preferably arranged to benormally disconnected from 1 the line'and to be connected therewith atwill through a suitable switch such as 28. The operator may have aspecial listening set, as indicated at 26 connected to the plug 23through an amplifier 26 and key 27* of usual construction, so thatthereturn currents through the line to central will be strengthened, Suchamplifiers or electron tube relays are Well known and need nosupervisory operator desires totest the qual ity of rece tion atsubstation A he plugs in on the hue at and de resses the ringing key 25whereupon the-su riber at A is signaled in theusual manner. The subscriber at A responding is instructed toreverse switch '21 and close rwitch 28, which thereupon disconnects the audio circuit of the detectorfrom the receivers 9 and connects it with the line extension 12 by wa ofconductors 29-30, cou ler 20 and switc 1 28, from whence the circuit isextended over the line conductors 3-'-4, line extension 56, jack andplugconnection 24--23 and listen ing-key 27 to the supervisory. operatorslistening set 26. The operator now listening in on the reception at thesubscribers substation. can ascertain the quality thereof and f. e findi ect e-se ju f th cause of such defect. For exampie he can discern theeffects of static, induction from power lines, cross talk from telephonelines, loose connections, etc.

In Fig. 2 I have shown a radio receiving circuit 8, connected to usualradio amplifierv and detector apparatus 9, which in turn is connected toan audio. amplifying 'set 9. connected to a modulator and transmittingset 9, having its output side terminating onswitching means such asplugs for connec-' tion to line circuits. The principle involved hereinis that of receiving at one frequency and relaying onto the subscribers.linesat a different frequency. The transmitter 9 and the receiver 89are. capable of being separately tuned, in a manner well understood inthe art, which is important as an element in this invention, because allmy subscribers instruments are standardized and flat tuned, that is, allare permanently tuned on the same frequency, which is the normaltransmitting frequency of the central otfice to which they are connectedfor service. The range of tuning is immaterial.

In Figs. 3 and 4 I have shown a form of 'subscri-bers d k instrumentembodying the elements, 18, 9, 20, 21, and'28 of. Fig. 1.

,The base 34 is hollow, and the detector set 18 with coupler 20, isarranged therein with suitable circuit connections through cords 42-43or through ordinary wiring. If cords are employed, the mutual capacity'of the conductors must be neutralized or minimized so as not tointerfere with re-' ception of the high frequency waves by the detectorset. On base. 34 is erected a column 32 carrying a switchhook 31,controlrling contacts within the column and 'shown n the diagram Fig. 1at 31. This hoolr when down disconnects'the entire set from line, andwhen up oonnectsthe set through wires 4243 to line. Twomanual switches21 and 28 are mounted on the base with contacts preferably within thesame, to control the listening set connection to 19 and the cut-back tocentral at 2930. A horn 33 is mountedon' the upper end of the col umn,with coupling nipples'33 arranged on opposite sides of 'its neck forreceiving the two head telephones lt) when the subscriber Y preferstolisten'in; that way. Tuning handles of any desired form may be alsoa-rranged on the outside of the'base as shown The foregoing arrangementis fiexibleand I will lend itself to various detailed forms ofsubscribers instruments. For example, the I cord connections of theradiophone set 18- 19 "may be dispensed with, as indicatedin Figure 5.The line connections 42 4.3 hero terminate in the primary coil 18",ofwhich theseconda'ry 18 is carriedon the instrument, conveniently in thebase thereof.-

Goil 18 may be enc qs d'i a c s ng s udi-v No. 47.547, filed August 1,1925,

nevasos cated in dotted lines, and the instrument adjusted withreference thereto either over it, or to one side. Several instrumentsand several secondaries may be used if desired with a s-ngle primary. Inthis case I have shown atube detector 18 withA and B batteries andtuning condenser all enclosed within the instrument body. Tubes suitablefor this purpose are commercially available, and small batteries arealsoon the market, either storage cells or dry batteries. In order toprovide a higher 13 battery voltage than is attainable with an enclosedbattery, a separate battery is provided for connection in series to thedesk set batterythrough a cord and a series-plu 'and'jack of. usual typeas indicated at 50 in Fig. In any case the receiver 19 is connected tothe instrument circuits through a cord, which for simplicity ofillustration is omitted in Figs. 3 and 4, but is indicated in Fig. 5.The mechanical vparts are numbered the same in Fig. 5 as in Figs. 3 and4, the outline only of the desk stand or casing being shown in dottedlines.

It is to be understood that super audio frequency or audio frequencyamplifying means, or both, may be added tothe receiving set withoutdeparting from the scope of my invention. Where the detached or loosecoupled form of instrument shown in Fig. 5 is employed, the arrangementof Fi 5 may be used, where the super audio lrequency amplification maybe between the line connections 42"413'Z1Ild the primary winding 18, andaudio frequency amplification means may be mounted on or in theinstrument unit. A further modification is that indicated in Fig. 5which is accomplished by connecting to the line wires 42-43 a completedetector set including super audio fre-' quency and audio frequencyamplifying tubes, detector coils and tuning devices, with the primarywinding of an vaudio frequency transformer or inductorium of anysuitable form arranged the same as coil 18. The instrument wouldthencarry the secondary of said inductorium, the receiver, and a Wireconnection to the receiver, only Various other modifications willsuggest themselves to those skilled in the art, and it is to beunderstood that I cnntemplate all such nonessential changes ormodifications as fall fairly within the scope of the appended claims. itdo not claim herein theiollowing: (1') A subscribers desk set shown in Fgs. 3, 4, 5, 5 and 5 nor the manner of coupling it to the line, the samebeing claimed in my copending divisional applications, ServNo.

681,992, filed December 21, 1923, and Ser.

(2) The broad idea of a circuit composed of a plurality of transmisisonlinks at difterent frequencies, relat d to the same line my inventionthe central ofiice over a subscribers line circult to the, subscriber'ssubstation, detector means at thesubstation for demodulating the same,means tr passing the rcsult-and audio frequency currents to line, andmeans at the central station responsive to said audio frequency curents,whereby a central station operator may listen in on the subscribersreceiving apparatus.

2. The combination with a telephone exchange system having a centraloffice, subscribers substations, and line circuits connectingthesubstations with the central office,- of means for transmittingmodulated super audio frequency carrier currents -from the centralotlice over a subscribers line circuitto the subscribers substation, ademodulating receiver at the substation, and means whereby an operatorat the central oifice may listen in directly on the output side of thesubscribers receiver over the line circuit.

3. The combination with a telephone exchange system having a centraloffice, subscribers substations and line circuits connecting thesubstations with the central office of means for transmittin modulatedsuper audio frequency carr1er-- currents over a subscr bers line circuitto the subscribers substation, detector means at the substation fordcinodulating the same, a telephone receiver at the substation connectedwith-theoulput side of the said detector, means for connecting saidoutput side of the detector with the line for transmittingaudio-frequency currents back over the line, and a supervisory circuitat the central oflice comprising. signaling, listening {and talkingmeans arranged to be. connected with any subscriber-s line for signalingand talking tothe subscriber and listening in on the audio-frequencycurrents sent back over the line from the substation.

4. The combination with a telephone exchange system having acentral'ofiicc, subsc1'ibers substations and line circuits connectingthe substations with the central office; of means for transmittingmodulated high frequency carrier currents over a subscribers line to thesubseribers substation, detectormeans at the substation for demodulatingthe same, means for connecting the output side of the subscribersdetector with the line, and supervisory audiorfre Ill) all

quency receiving and amplifying means atthe central station arranged tobe connected with the subscribers line. i

5. In a telephone exchange .system, acentral office, a plurality ofsubscribers substations, l'ine circuits connecting the substations withthe central office, means at the central office for establishing aconnection for telephone currents between any two subscriberssubstations, means also at the central office for transmitting modulatedsuperaudio frequency currents over the line circuits in multiple to thesubstations, and means at the substations to demodulate the same and toreproduce the sound Waves represented thereby, the receiving apparatusat all said subscribers stations being standardized and having a tuningoperatively fixed to one and the same predetermined frequency, and thetransmitting apparatus being adjustable for tuning to said frequency.

6. The combination with a telephone exchange system having a centraloffice, sub; scribei's substations and "lines connecting the substationswith the central otlice, radio receiving instruments connected to theline circuits at the subscribers stations, and cooperating tunedsuperaudio current transmitting 7 means at the central station saidreceiving instruments being tuned to the frequency of the central officetransmitting means and means at the central ofice for receiving radiocommunication at any one of a plurality of frequencies and relaying itat the frequency of the central oitice transmitting means.

' YVThe combination With a telephone exchange system having a centraloffice, subscribers substations and lines connecting the substationswith the central office, radio receiving instruments connected to theline circuits at the subscribers stations, and cooperatingtuned'superaudio current transmitting means at thecentral statiomsaidreceiving instruments being tuned to the frequency of the central-oiiice transmitting means, and means at the central otlice forreceiving radio communication at another frequency and relaying it atthe frequency of the central otlice transmitting means.

8. The combination with a telephone exchange system having acentralotiice, subscribers substations, and line circuits connecting thesubstations with the central office, carrier current receivinginstruments connected to the line circuits at the subscriberssubstations, and tuned carrier current transmitting means at the centralotlice, said" receiving instruments bein' tuned to the frequency of thecentral 0 cc transmitting means and being standardized, and means at thecentral office for receiving modulated carrier waves radiated at variousfrequendiated at. various-frequencies and for relaying the samemodulations over the subscribers lines on a-carrier Wave of thefrequencyof the central office transmitting means, said central officereceiving means being equipped with variable tuning devices forselective reception from sending stations employing differentfrequencies in transmitting, and

separate relay tuning means for maintaining the relay transmitting meanstuned to the constant frequency common to the sub scribers receivingmeans.

10. lln a telephone exchange system, subscribers station circuits, acentral oiiice, line circuits connecting them, the subscribers stationcircuits being coupled-to said line circui s and said line circuitsbeing adapted to carry modulated high frequency Waves into thesubscribers stations, the line circuits being all tuned to the samefrequency and forming a plurality of tuned paths in parallel withrespect to the central office, means for controlling the subscribersstation circuits of such nature that operation thereof tends to cause(lotuning of the tuned paths, and means in the connection between saidcontrol means and the line circuit for:

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